John
From the wording of your post, I get the impression that you are somewhat new to the world of MIDI, so I have responded from that viewpoint. Please forgive if I have misread that:
"TRACKS" are INTERNAL to their own device. For instance, the MO8 sequencer will record data to its own "TRACKS" and Cubase will record data to its own "TRACKS", and so forth, and these "TRACKS" are analogous to the "TRACKS" in old tape transport systems. Now, when we send MIDI data between devices, say between the MO8 and Cubase, the communications medium is divided up into "CHANNELS" instead of "TRACKS". Typically it goes on a one-for-one basis. That is, the MO8 would transmit its Track-1 on Channel-1 and Cubase would receive Channel-1 into its Track-1, but you do not HAVE to do that. You CAN shuffle the order, if you want - say - Track-2-to-Channel-5-to-Track-7, but its usually best to try to keep it one-to-one as much as possible in order to keep everything straight. So, when it comes to sending recorded data from the MO8's sequencer to Cubase, you need to tell the MO8 which "TRACKS" to send on which "CHANNELS" and you need to tell Cubase which incoming "CHANNEL" to feed to which one of its "TRACKS". Most keyboard sequencers do their end for you. They usually default to a one-to-one TRACK-CHANNEL set up, but most DAW's default to receiving all incoming "CHANNELS" to "TRACK" 1, so that would need to be changed for each incoming channel. The current MIDI standard provides for only 16 "CHANNELS", and most keyboard sequencers are designed to match this with 16 "TRACKS" or "PARTS", although some high-end systems provide a MIDI-A and a MIDI-B with 16 "TRACK/CHANNELS" each, but most DAW software now offers anywhere from 16 to 32 to 48 to 64 or unlimited "TRACKS", so some TRACK/CHANNEL number shuffling with these systems is inevitable. The DAW software will show you on a track-by-track basis which "CHANNEL" each "TRACK" is tied to. You just need to know where to look for it and how to change it, as each DAW is a little different in that respect.
Now, when it comes to playing from the keybed directly into a DAW, the setup of the keyboard becomes a little more involved. If you are just playing a single (full keyboard part), you just set up the keyboard to send on CHANNEL-1 and tell your DAW which TRACK to record it to, but if you can 'SPLIT" the keyboard, the two sections become "PARTS", and you need to tell both the keyboard and the DAW what to do with the MIDI data for those two "PARTS". Normally you want to keep them separate, as they are going to use different tones in the sound module. So, for a one-to-one set up, you would need to tell the MO8 to transmit PART-1 (the right hand or upper data) on CHANNEL-1 and PART-2 (the left hand or lower data) on CHANNEL-2. Then you would need to tell Cubase to record the data to its TRACKS 1 and 2 respectively. From what you are describing, it sounds like this is the step that has not been done on your system. It sounds like Cubase is recording everything to (probably) TRACK-1. You need to check the section in your Cubase manual for assigning (tying) different TRACKS to different CHANNELS and how to ARM the TRACKS for recording. With an ARRANGER, it gets a lot more complicated, because there are UPPER, LAYER (or HARMONY), DRUM, BASS, and two or three CHORD (accompaniment) PARTS that all have to be accounted for and sent on the correct "CHANNELS" and received to the correct "TRACKS". If you are generating MIDI data to work with General MIDI (GM) compatible systems, TRACK-10 is reserved for the DRUMKIT voices and TRACK-16 is (optionally) reserved for PERCUSSIVE and SFX sounds.
AND . . . now that we have all of our TRACKS and CHANNELS sorted out, when we save MIDI data to a FILE on some type of storage media, we run into a new twist. If we save to a TYPE-0 MIDI file, all of the "TRACKS" data are saved to a SINGLE CHANNEL and when data from that file is read or played, the TRACK-TO-TRACK data is fanned back out just like it is supposed to be. If we save to a TYPE-1 MIDI file, then the "TRACKS" are saved to separate "CHANNELS" on a one to one basis, but this has NOTHING to do with how the MIDI data (TRACKS) is handled "WITHIN THE SEQUENCERS". I just bring it up here to explain the difference between the two types of FILES.
Hope this helps - Good luck !